Boston Marathon bombing: A year after the marathon bombings, Boston perseveres

People pause at the memorial site in Copley Square for the deadly attacks on the Boston Marathon on Boylston Street April 30, 2013 in Boston, Massachusetts.

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"United, we will always persevere." That was the message Massachusetts shared with the nation and the world Tuesday, on the anniversary of twin bombings that turned last year's Boston Marathon from a celebration into a day of horror.

The state tweeted those words, along with an image of both the U.S. and Massachusetts flags, and the hashtag #BostonStrong.

Mayor Tom Menino, Gov. Deval Patrick and Vice President Joe Biden are expected to echo that message Tuesday afternoon at a tribute marking the anniversary. The Boston Pops and a children's choir will take part. Near the end -- scheduled for 2:49 p.m. ET -- will be a moment of silence, followed by church bells tolling and a flag-raising ceremony.

On April 15, 2013, the Patriots Day bombings killed three people, including an 8-year-old boy, and wounded at least 264 others. The city then underwent days of fear as the two identified suspects, the Tsarnaev brothers, were on the run. Police say they killed a Massachusetts Institute of Technology police officer in the process, and then Tamerlan Tsarnaev was run over by his younger brother, Dzhokhar, as they battled police. Dzhokhar Tsarnaev has pleaded not guilty to 30 counts and is scheduled to go on trial in November.

MIT police plan to mark the death of officer Sean Collier in a remembrance ceremony Friday.

A year after the bombings, families of the victims are struggling to come to terms with the loss.

"She had that special, I don't know what it is, that special thing about her," says Lillian Campbell, grandmother of 29-year-old Krystle Campbell, one of the three people killed. "And you felt happy around her because she was always laughing and bubbly. I loved her."

Some victims injured in the attack are showing their perseverance by planning to take part in this year's marathon, scheduled for Monday -- even victims who suffered severe injuries.

"Last year I was on the ground at the finish line. This year I'll be running across it," says Kevin White. "It kind of proves to people that evil isn't going to win." White, then 34, had shrapnel through his legs a year ago. His 71-year-old father, Bill, lost a leg.

Authorities have announced extensive security plans for this year's marathon, which is expected to bring in $176 million for the Boston area's economy.

Brothers Paul and J.P. Norden each lost a leg in the attack last year. On Tuesday, they began a trek -- walking the entire 26.2-mile marathon route, along with family and good friends. "I feel so blessed," their mother Liz said in a Facebook post, adding that she couldn't be prouder.

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